Heretofore self-tapping fitting assemblies, such as service tees, nipples, saddles, or the like have been utilized in fluid distribution systems, such as water, gas, or the like, in connecting a main to a secondary main or service line while the main is dry or while the main is under pressure of the fluid, this latter connection being made without the escape of the fluid from the main to atmosphere. Such prior arrangements have used drilling machines connected to the fittings through which coupon cutters, drills or the like were advanced through a valve and through the fitting to form a hole in the main.
In most of the prior art devices, the self-tapping fitting, in most instances, was permanently attached to the main at a position where the hole in the main was to be tapped. More recently and with the advent of the use of plastic pipe, efforts have been made to at least preliminarily attach the fitting to the main and then form the hole in the main and provide an internal connector between the main and the fitting for at least assisting in holding the fitting permanently on the main and in some instances providing the primary hold means between the main and the fitting.
In one such recent effort, the through bore of a fitting was threaded interiorly for receiving a tapping tool for cutting a coupon from the main, the tapping tool being provided with exterior threads to cooperate with the threads of the through bore for advancing the same and a second set of exterior threads for retaining the tapping tool as an internal connector between the main and the fitting. In this type of an arrangement the coupon, which often times remains tightly gripped or wedged in the cutting tool was difficult to remove from the cutting tool, especially when a thick wall pipe was tapped.
Still other arrangements were contemplated for providing an internal connector between the main and the self-tapping fittings. In one such arrangement a coupon cutter member was utilized to form the hole by cutting a coupon from the main and then an insert was axially driven into the hole and its lower end had to then be flared outwardly to prevent the insert from being blown out of the hole when the service line was put into operation. The insert was provided with barbs on its exterior for the purpose of biting into both the fitting and the main and even with such barbs the lower edge of the tubular insert still had to be flared outwardly to make a permanent connection.
Still further efforts were made to provide an internal mechanical fastening means by utilizing the material being removed in the forming of the hole as a mechanical fastening means between the main and the fitting, the material being swaged outwardly of the main into the through bore of the fitting. Where the material in and of itself was not of sufficient strength to function fully as a mechanical fastening means, a reinforcing sleeve was inserted into the interior of the hole and the upset material defining the finished hole.
The prior art arrangements were somewhat limited in their use in that they could only be used on pipes of certain soft materials such as plastic pipes or asbestos cement pipes or soft metal pipes and in most instances the pipes had to be of thin wall construction.